Create a movieClip on your stage and name it mcDot.
Delete the mcDot from your stage.
Open the library panel, right-click the mcDot clip then select properties:
Under the "Linkage" category check "Export for ActionScript"
Give the class the name "Dot". Make sure it is capitalized.
var dot:Dot= new Dot;
addChild(dot);
dot.x=stage.stageWidth/2;
dot.y=stage.stageHeight/2;
http://asgamer.com/2009/flash-game-design-basics-adding-library-objects-to-stage-with-as3
CyanBlue